Many medical procedures involve the removal of undesirable material from various tubular structures within the human body. Such materials may be of the body's origin or man-made. Examples include, but are not limited to, blood clots in the arteries and veins, foreign bodies introduced by surgery that have migrated or become dysfunctional and stones in the biliary or urinary systems. While these unwanted objects may be removed by surgical procedures, interventional radiological techniques have been developed to provide a less-invasive alternative.
One type of interventional radiological technique involves the use of a snaring device that is introduced into the tubular structure by a catheter or sheath and positioned by a guidewire with endoscopic or fluoroscopic guidance. The snaring devices commonly feature a wire cage-like structure positioned upon their distal end portions that may be flexed to receive the target object. Once the snaring device is in position, it is operated remotely by the physician to capture, and in some instances crush, the target object. The object may then be withdrawn from the body through the catheter or sheath insertion site or left to be ultimately washed out of the body by normal body fluids. Examples of such devices are presented in U.S. Pat. No. 4,198,960 to Utsugi, U.S. Pat. No. 4,927,426 to Dretler and U.S. Pat. No. 5,496,330 to Bates et al.
While such devices are effective, they do not feature a means for affirmatively trapping an object. As a result, there is always a danger that an object will become unintentionally dislodged from the snare prior to its removal. The object would then be free to migrate through the tubular structure which could cause severe medical complications.
Other methods of removing objects from the tubular structures of the body vary considerably depending upon the specific object to be removed and the tubular structure involved. For example, a medication may be injected into a vein or artery in an attempt to dissolve a blood clot. Examples of suitable medications include urokinase, streptokinase, t-PA, etc., with or without a blood plasma or saline carrier. U.S. Pat. No. 4,692,139 to Stiles discloses a catheter suitable for performing such a procedure.
While effective, the infusion of such medications has associated risks. More specifically, there may be a precipitation of bleeding at the catheter insertion site or in the stomach or brain. Furthermore, such medications are extremely costly and a great deal often is often consumed during their administration in that the patent must be closely monitored for complications.
As disclosed by U.S. Pat. No. 5,092,839 to Kipperman, a balloon catheter may be used to remove thrombus and plague from a coronary artery. The '839 patent discloses a device featuring a balloon catheter disposed through the lumen of a guide catheter, the latter of which features an expandable distal tip. Once the device is positioned in the artery, the balloon is inflated to expand the distal tip of the guide catheter. The balloon is then deflated and the distal tip of the guide catheter retains its expanded shape. The balloon catheter is then extended out from the distal tip and beyond the occluded portion of the artery and is once again inflated. The inflated balloon is then retracted back into the guide catheter, carrying with it residual pieces of thrombus and/or plaque which has been dislodged from the artery wall.
A disadvantage of the apparatus and method of the '829 patent, however, is that, in order to properly expand the distal tip of the guide catheter, the balloon must be precisely positioned. Furthermore, once the distal tip of the guide catheter is expanded, it cannot be contracted. As a result, the physician faces increased difficulty when attempting to remove the distal tip from the body.
For the removal of stones from the biliary or urinary systems, lithotripsy devices have been developed. As described in U.S. Pat. No. 4,957,099 to Hassler and U.S. Pat. No. 5,658,239 to Delmenico, these devices propogate shock waves through a fluid medium and into the patient's body so that stones are pulverized. Although effective, lithotripsy devices are expensive, complex and cumbersome.
Patients who are temporarily immobilized because of recent surgery or trauma face an increased risk of blood clot formation in the veins of the legs. As a result, in such situations, it is desirable to filter the inferior vena cava, that is, the main vein draining the abdomen and lower extremities of the body, to prevent the migration of these blood clots.
Examples of existing vena cava filters are presented in U.S. Pat. Nos. 4,619,246 to Molgaard-Nielson et al., 5,133,733 to Rasmussen et al. and 5,397,310 to Chu et al. Filters of the type disclosed by these patents all are anchored to the interior wall of the vena cava by way of metal hooks or legs. As a result, it is difficult, if not impossible, to remove such devices from the vena cava without causing severe damage to the vena cava's interior wall.
It follows that such devices must be permanently placed in the inferior vena cava without the option for retrieval even though a patient's period of risk may be limited. Health care providers using these devices thus are often faced with the difficult decision whether to permanently implant a device, even though the period of risk is limited, or, alternatively, to allow the patient to be at risk of the occurrence of a potentially fatal event. Furthermore, in the case of patients with recent trauma or planned surgery, the absence of clotting may be inaccurately indicated. As a result, the health care provider will often decide against inserting a permanent device, and hence the patient is exposed to risk.
In response to this problem, devices for temporary inferior vena cava filtration have been developed. Examples of such a device is disclosed in U.S. Pat. Nos. 5,329,942 to Gunther et al. and 4,662,885 to DiPisa. Like the vena cava filters discussed above, however, the filters of the '942 and '885 patents do not provide a means for temporarily adjusting the size of the filter opening once the filter is positioned within the vessel. Such a feature would be invaluable in allowing the devices to be used to retrieve trapped clots.
Finally, U.S. Pat. No. 5,423,851 to Samuels discloses an apparatus employing an inflatable cuff to secure an endoluminal device, such as a filter, within a tubular structure of the body. This apparatus, however, is designed for permanent placement of devices within tubular structures via radially projecting barbs and thus is not well-suited to removing objects from the body.
Accordingly, it is an object of the present invention to provide a method and apparatus for removing objects from tubular structures of the body that is minimally invasive.
It is another object of the present invention to provide a method and apparatus for definitively trapping objects in tubular structures of the body.
It is another object of the present invention to provide a method and apparatus for removing objects from tubular structures of the body that does not require the use of medications.
It is still another object of the present invention to provide a method and apparatus for removing objects from tubular structures of the body that may be expanded after insertion and retracted prior to removal.
It is still another object of the present invention to provide a method and apparatus for removing objects from tubular structures that does not require expensive, complex or cumbersome equipment.